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African Skimmers…Skimming

This diary entry took place at Liwonde National Park - Malawi

The languid Shire River, Malawi’s largest, recently delivered my best skimmer experience yet. All the key ‘ingredients’ to a good sighting (and photograph) magically came together: Skimmers actually skimming nonstop around our boat in very close proximity, actively vocalising and all in amazing afternoon light.

The African skimmer, Rhynchops flavirostris, is a distinctive bird, its striking black upperwings, pure white belly and bright yellow-orange bill as diagnostic as its unique feeding behaviour. Individuals or flocks fly low in an effortless, buoyant style over Africa’s water systems, dipping their bills into the water in a skimming motion designed to catch small fish close to the surface. Once a fish – usually small fry less than eight centimetres in size – is caught, the bird’s head and neck snap back in flight and the fish is secured in the bill. All of this takes place at speeds of up to 30 kilometres per hour, with most feeding occurring at dawn and dusk.

While we were at Liwonde, it was also incredible to hear this species calling well after dark and when I ventured outside with a torch (tip-toeing amongst hippo that were foraging out of the water, I might add!) they were still seen skimming, calling and feeding under the dim moonlight just beyond the torchlight beam. This perhaps shows that their feeding technique has a high sensory or touch element, more so than sight.

Such efficient feeding belies the complexity of the species’ evolutionary adaptation. The bill is a unique shape. The lower mandible – that part of the bill that skims the surface of the water – is nearly 40% longer than the upper. It is also incredibly thin and fused at the tip, with a rudder-like extension below this, so as to be aquadynamic and able to carve through the water without affecting flight.

The African skimmer needs intact, pristine ecosystems and when these are available, it does well in what’s left of the most remote and unspoilt wilderness areas on the African continent today. As an ecological indicator, their abundance in a given locale should be seen as a real success – as the skimmer is regarded as generally uncommon with a total population (on a decreasing trend) estimated at only 15 000 - 25 000 birds.

Although they are a widespread species in sub-Saharan Africa, broad lowland rivers and lakes with exposed sandbars for breeding are critical for their survival and the species moves widely in search of optimum nest sites. Breeding takes place during the dry season when rivers are at their lowest and sandbars most exposed – mainly from July to November in southern Africa.

However, African skimmers are sensitive to disturbance (mainly at nesting sites) and habitat change. This leaves the species largely limited to protected areas in Africa where ecosystems continue to function as intended, and where rivers have not been impacted by damming or other hydrological schemes: in other words, pure wilderness. Egg- and chick-collecting by subsistence fishermen, trapping of adults, and general disturbance by humans, cattle and recently increased boat traffic (including recreational fishermen using powerboats) pose serious problems in some areas.

Skimmers are classified in the Rynchopidae family which comprises only three species of tern-like birds. Apart from the African skimmer, the black skimmer is found in the Americas while the Indian skimmer is found in south Asia.

Lady Luck was clearly on my side that day, as when we went out the following afternoon, under almost identical conditions, we did not enjoy such a sighting again.